RE: twin engine size????
Hi!
20cc gas engines is way to big!
I would use either 10 or 15cc two strokes (.61 or .91)! Four strokes doesn't sound right on a plane like that!
Also forget 3-blade props! They would be too small, not scale like anyway, if using 10-15cc engines! Go with AP or RAM props! 2-blades for best performance!
12x6 , 13x4 or 13x5 is using 10cc engines and 14x6 or 15x4 if using 15cc two strokes (at sea level).